var mathId = document.getElementById("show"); //选择公式识别范围
        MathJax.Hub.Config({
        showProcessingMessages: false, //关闭js加载过程信息
        messageStyle: "none", //不显示信息
        extensions: ["tex2jax.js"],
        jax: ["input/TeX", "output/HTML-CSS"],
        tex2jax: {
            inlineMath:  [ ["$", "$"] ], //行内公式选择$
            displayMath: [ ["$$","$$"] ], //段内公式选择$$
            skipTags: ['script', 'noscript', 'style','textarea', 'pre','code','a'], //避开某些标签
            ignoreClass:"comment-content" //避开含该Class的标签
        },
        "HTML-CSS": {
            availableFonts: ["STIX","TeX"], //可选字体
            showMathMenu: false //关闭右击菜单显示
        }
        });
        MathJax.Hub.Queue(["Typeset",MathJax.Hub]);